Compiled by the International Food Policy Research Institute (IFPRI), a US think-tank, the index used three measurements to compile its ranking: child malnutrition, child mortality, and the estimated proportion of people without access to enough food.

"Alone, each indicator has limitations, but put together, they give us a much more complete picture of the state of hunger around the world," Index author Doris Weismann said.

Failing harvests

IFPRI's findings were echoed by the UN Food and Agriculture Organization (FAO).

The organisation's Crop Prospect and Food Situation Report last week described the crisis in the Darfur region of Sudan as the "most pressing humanitarian problem".

It added: "The already precarious food supply situation may worsen if deteriorating security disrupts the main harvest due to start in the coming weeks."

The report highlighted 40 nations in Africa, Asia and Central America that were facing food emergencies because of poor cereal harvests, and were likely to need help from the international community.

The theme of this year's UN World Food Day was "investing in agriculture for food security", FAO director general Jacques Diouf declared.

"Recently, there has been a significant revival in lending for agriculture," he said in a speech to launch the annual event.

"Debt forgiveness programmes... have begun to release national resources for investment in agriculture. But much still remains to be done."

Dr Diouf said estimates showed that achieving the Millennium Development Goal of halving world hunger by 2015 would require an extra investment of $19bn (£10bn) in agricultural projects, and a further $5bn (£2.7bn) for immediate food aid efforts.

IFPRI hoped the Global Hunger Index would help focus attention on delivering the 2015 goal.

"We hope to mobilise the political will to speed up urgently needed progress in the fight against hunger in those countries that rank the worst," IFPRI director general Joachim von Braun said.

He called on governments and civil society to deliver the necessary investment: "But we cannot be satisfied merely to cut it in half, hunger must be eradicated completely."